Condensation, damp and mould
Is your home damp? Damp can cause mould on walls and furniture and make window frames rot. Damp cold housing encourages the growth of mould and mites, as mites feed on moulds and can increase the risk of respiratory illnesses in some people. Some damp is caused by condensation. The following information explains how condensation forms and how you can keep it to a minimum, so reducing the risk of dampness and mould growth.
First steps against condensation
You will need to take proper steps to deal with the condensation, but meanwhile there are some measures you can take right away.
Wipe down the windows and sills every morning. Wring out the cloth rather than drying it on a radiator.
Condensation channels and sponge strips can be bought at DIY shops. They are fitted to windows to collect the condensation and thus help prevent window frames from rotting and avoid damp forming under sills. Care must be taken to fit these devices properly.
First steps against mould
First treat the mould already in your home. If you deal with the basic problem, mould should not reappear.
To kill and remove mould, wipe down walls and window frames with a fungicidal wash which carries a Health and Safety Executive 'approval number'. Follow the manufacturer's instructions precisely. Dry-clean mildewed clothes, and shampoo carpets. Disturbing mould by brushing or vacuum cleaning can increase the risk of respiratory problems.
After treatment redecorate using a good quality fungicidal paint to help prevent mould. Note that this paint is not effective if covered with ordinary paints or wallpaper. When wallpapering, use a paste containing a fungicide to prevent further mould growth.
The only lasting way of avoiding severe mould is to eliminate dampness.
Is it condensation?
Condensation is not the only cause of damp. It can also come from:
- Leaking pipes, wastes or overflows
- Rain seeping through the roof where a tile or slate is missing, spilling from a blocked gutter, penetrating around window frames, or leaking through a cracked pipe
- Rising damp due to a defective damp-course or because there is no damp-course
These causes of damp often leave a 'tidemark' and you should have the necessary repairs carried out to remove the source of damp.
If your home is newly built it may be damp because the water used during its construction (eg. in plaster) is still drying out.
If your home is damp for any of these reasons it may take weeks of heating and ventilating to dry out. Hiring a dehumidifier will help.
If you do not think the damp comes from any of these causes, it is probably condensation.
What is condensation?
There is always some moisture in the air, even if you cannot see it. If the air gets colder it cannot hold all the moisture and tiny drops of water appear. This is condensation. You may notice it when you see your breath on a cold day, or when the mirror mists over when you have a bath.
Condensation occurs mainly during cold weather, whether it is raining or dry. It does not leave a 'tidemark'. It appears in places where there is little movement of air. Look for it in corners, on or near windows, in or behind wardrobes and cupboards. It often forms on north-facing walls.
How to avoid condensation
These four steps will help you reduce the condensation in your home.
1. Produce less moisture
Some ordinary daily activities produce a lot of moisture very quickly.
Cooking: To reduce the amount of moisture, cover pans and do not leave kettles boiling.
Paraffin and portable flueless bottled-gas heaters: Do not use these heaters as they put a lot of moisture into the air - one gallon of gas or paraffin produces about a gallon of water. Try to find alternative means of heating.
Washing clothes: Put washing outdoors to dry if you can. Or put it in the bathroom with the door closed and the window open or fan on. It is best to fit a fan that can be switched to run continuously for clothes drying. If you have a tumble dryer make sure you vent it to the outside (unless it is the self-condensing type). DIY kits are available for this.
2. Ventilate to remove the moisture
You can ventilate your home without making draughts.
Some ventilation is needed to get rid of moisture being produced all the time, including that from people's breath. Keep a small window ajar or a trickle ventilator open all the time if possible, and especially when someone is in the room.
You need much more ventilation in the kitchen and bathroom when cooking, washing up, bathing and drying clothes. This means opening the windows wider. Better still, use a humidistat-controlled electric fan (these come on automatically when the air becomes humid and are cheap to run).
Close the kitchen and bathroom doors when these rooms are in use even if your kitchen or bathroom has an extractor fan. It will help to draughtproof these doors. Doing this will help stop the moisture reaching other rooms, especially bedrooms, which are often colder and more likely to get condensation.
Allow space for the air to circulate in and around your furniture. Open doors to ventilate cupboards and wardrobes. Leave space between the backs of wardrobes and the wall. Where possible, position wardrobes and furniture against internal walls, ie. walls which have a room on both sides, rather than against outside walls.
When you have a curtain or blind drawn, it makes the surface of the window cooler and increases condensation, especially with single glazed windows. Trickle ventilators can help reduce the problem. If you replace your windows at any time, make sure they are double glazed and fitted with trickle ventilators.
3. Insulate and draughtproof
Insulation in the loft, cavity wall insulation and draughtproofing of windows and outside doors will help keep your home warm and you will have lower fuel bills as well. When the whole home is warmer, condensation is less likely.
- Do not block permanent ventilators
- Do not completely block chimneys (leave a hole about two bricks in size and fit a louvred grille over it)
- Do not draughtproof rooms where there is a fuel burning heater (eg. gas fire) or cooker
- Do not draughtproof windows in the bathroom or kitchen
If you live in a house, insulating your loft is a cost-effective way of cutting heating costs. Remember to draughtproof the loft hatch but do not block any eaves ventilation. Cavity wall insulation is also an effective way of cutting heating costs. Many properties, however, are built without suitable cavities. If you are in doubt, you should seek the advice of a building professional who will advise you on the need for a building warrant.
Secondary glazing of windows reduces heat loss and draughts but you must ensure that there is some ventilation and adequate means of escape in an emergency such as a fire. Remember that any alteration to your windows, including their replacement, must meet the relevant requirements of the Building Regulations. You should consult you local authority before any work is undertaken.
4. Heat your home a little more
In cold weather, the best way to keep rooms warm enough to avoid condensation is to keep low background heating on all day, even when there is no one at home. This is very important in flats and bungalows and other dwellings where the bedrooms are not above a warm living room. If you have central heating set it to provide background warmth in all rooms including unused rooms.
Otherwise install suitable thermostatically-controlled heaters where necessary (do not use paraffin or flueless bottled gas heaters for this purpose). The thermostats will help control heating and costs. Remember to provide background ventilation at the same time.
Dehumidifiers will help dry out damp in newly built houses. They can also help reduce condensation but they are of limited use in cold damp rooms.
Points to remember
Produce less moisture
- Cover pans
- Dry clothes outdoors
- Vent your tumble dryer to the outside
- Avoid using paraffin or flueless bottled gas heaters
Ventilate to remove moisture
- Ventilate all the time, especially when someone is in
- Increase ventilation of the kitchen and bathroom when in use and shut the door
- Ventilate cupboards, wardrobes and blocked chimneys
Insulate and draughtproof
- insulate the loft
- draughtproof windows and external doors
- consider cavity insulation
- consider secondary glazing
- find out if you are eligible for a grant or other help
Heat your home a little more
- if possible, keep low background heat on all day, with background ventilation
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